Tuesday, August 16, 2016

Wind Storm and Cyclone Living science answer class7

A. Multiple Choice Questions:Wind Storm and Cyclone Living science answer class7
1. Air exerts pressure in

a. all directions

b. downward direction only.

c. upward direction only

d. sideways only.

2. Low atmospheric pressure exists on the earth in which of the following latitudes?

a. at the equator only

b. at 30° N and S

c. at the Poles

d. at the equator and at 60° N and S

3. Which of the following are not associated with cyclones?

a. strong winds

b. heavy rains

c. tidal waves

d. volcanic eruptions

4. Development and movement of cyclones are studied by the

a. Indian Postal Department.

b. Indian Forensic Department.

c. Indian Meteorological Department.

d. Central Investigation Department.

5. Which of the following states of India is most likely to be hit by a cyclone?

a. Punjab

b. Madhya Pradesh 

c. Andhra Pradesh

d. Jammu and Kashmir

6. A piece of plywood is kept on a table. You have to lift it from the table by blowing air over it at very high speed from a powerful fan. In which direction will you blow air?

a. in the upward direction

b. in the downward direction 

c. sideways

d. in the upward direction below the table 

7. The fact that, increased wind speed results in reduced air pressure is known as

a. Galileo principle.

b. Bernoulli principle.

c. Newton principle.

d. Einstein principle.

8. Which of these best describes a tornado?

a. strong thunderstorm

b. the eye of a cyclone

c. rotating funnel of high speed wind 10-15 km across

d. rotating funnel of high speed wind 10-200 m across 

Ans. 1. a        2. d              3. d        4. c         5. c                6. c          7. b             8. d

B. VERY SHORT-ANSWER QUESTIONS: Give one-word answers.
1. Does air temperature increase or decrease as you go up in the atmosphere?

2. Does air pressure increase or decrease as you go up in the atmosphere?

3. A rubber sucker pressed on flat surface sticks to the surface because air pressure inside it is __________ (more/less) than the air pressure outside.

4. The faster the air moves, the _______________ (greater/smaller) is the pressure.

5. When air expands, it rises tip. True or false?

6. Where is the air pressure higher — at the equator or at the Poles?

7. Monsoon winds flow because of uneven heating of land and _____________.

8. Lightning is an electric spark between clouds. True or false?

9. Calm conditions do not prevail anywhere in the cyclone. True or false?

10. Cyclonic winds tend to circulate around the _______________ of the cyclone.

Ans: 1. decrease 2. decrease 3. less 4. smaller

5. true 6. Poles 7. sea/water 8. true 9. false 10. eye

C. SHORT-ANSWER QUESTIONS: Answer in a sentence or two.

1. Name any four natural hazards.

Ans: Four natural hazards are earthquakes, floods, droughts and cyclones

2. In which direction does air exert maximum pressure?

Ans: Air exerts pressure in all directions.

3. The speed of wind in a region suddenly increases. How does this affect the pressure in the region?

Ans: . This will reduce the pressure in the region.

4. Why does heated air rise up?

Ans: When air is heated, it expands. This causes it to become lighter than the surrounding cooler air thus it rises in

5. What causes monsoon winds?

Ans: Monsoon winds are caused by uneven heating of land and sea.

6. What causes lightning during a thunderstorm?

Ans: Static electricity is produced due to the collisions between water droplets and ice crystals in atmosphere. This causes huge sparks between clouds or between a cloud and the ground in the form of lightning during a thunderstorm

7. Why does a cyclone become weak once it hits land?

Ans: The cyclone becomes weak once it hits land due to friction with land and shortage of moisture.

8. What causes a tornado to be formed?

Ans: A tornado is formed when a funnel-like column of cold air sinks down from a storm cloud. Warm air from the surface rises up, whirls around it and causes very high speed winds.

D. LONG-ANSWER QUESTIONS: Answer in about 50 words.

1. Explain why a rubber sucker pressed on a smooth surface gets stuck to the surface.

Ans: Rubber sucker when pressed against a flat smooth surface, forces air, out between the smooth surface and the sucker. This reduces air pressure in the space between the sucker and the smooth surface. There is greater air pressure outside. Hence, this air pressure outside firmly presses the rubber sucker to the smooth surface.

2. Describe an experiment to show that increased wind speed leads to reduced air pressure.

Ans: We have to tape cotton threads to two tennis balls and hang them 2-3 cm apart from each other at the same height.

Now, we should blow air between them using a drinking straw.

Harder we blow, the closer the balls come to each other. This happens because, when we blow between the two balls, the air pressure between them reduces

3. a. In which direction does wind blow between the equator and latitude 30° N? Why?

Ans: The wind blows towards the equator. This happens because the regions close to the equator get the maximum heat from the sun. The air near the earth's surface becomes warm and rises, producing a low pressure region. Cooler air from either side of the equator up to a latitude of about 30° rushes in to take its place.

3. b. Why does the wind swerve to one side instead of blowing straight?

Ans: If the earth had stood still, these winds would have blown straight. But as the earth rotates, the winds in the Northern Hemisphere swerve to the right, and the winds in the Southern Hemisphere swerve to the left.

4. What are the hazards associated with a cyclone?

Ans: The hazards associated with a cyclone are strong winds, heavy rains, tidal waves and floods. The high speed winds of tropical cyclones are accompanied by heavy rains and huge sea waves. Flooding is caused by the huge sea waves as they hit the coast, and the accompanying rain further worsens the situation. Trees get uprooted, houses collapse, and telecommunication lines get disrupted leading to heavy loss of life and property.

5. Describe the 'eye of a cyclone'.

Ans: At the centre of the cyclonic storm is a calm, cloudless area. This is called the eye. Its diameter may vary from 10 km to 30 km. There is no rain here, and the winds are fairly light.

6. How is the forecasting of cyclones done in India?

Ans: The Indian Meteorological Department studies the development and movement of cyclones. This is done with the help of INSAT satellite and chain of Cyclone Detection Radars (CDRs) installed along the coastal belt of India. These radars can locate and track an approaching cyclone within a range of 400 km.

7. What precautions are needed in the cyclone-prone areas?

Ans: Precautions needed for the cyclone-prone regions are:

(i) Listen weather bulletins regularly in radio and TV.

(ii) Store enough food articles in waterproof bags. Also store safe drinking water.

(iii) As soon as a warning is sounded, secure home well or move to the safer places.

(iv) Do not venture into the sea.
8. Draw a labelled diagram of the structure of a cyclone. Mark the direction of winds surrounding the eye. 

HOTS QUESTIONS: Think and answer.

1. You may have seen holes made in huge hoardings. Why are these necessary?

Ans: Holes are necessary in hoardings to reduce the air pressure on them when the wind blows, as much of the air passes through the holes.

2. News item in a newspaper: 'A cyclone, that started in the desert of Rajasthan, hits Delhi today' Is the news item correct? Give reasons.

Ans: No. We can not expect a cyclone to be formed in the desert of Rajasthan as it usually forms over the sea.

3. In winter, in regions near the equator, why does wind blow from land to the sea?

Ans: In winter the sea near the equator is warmer than the land. As the air above the sea rises, the air above the cooler land blows to take its place.

4. Suppose the earth rotated from east to west, instead of from vest to east. How would this affect the pattern of wind circulation on the earth?

Ans: If the earth rotated from east to west, instead of west to east, the winds in the northern hemisphere would swerve to the left instead of right, and the winds in the southern hemisphere would swerve to the right instead of left.

5. The figure shows wind blowing at high speed in a narrow region. Will the pressure be high or low at A, B and C?

Ans: The pressure would be low at B and C. However at A, directly in the path of the wind, the pressure would be high.

7th Wind Storm and Cyclone Living science question answer Download File

Wind, storms and cyclones class 7 solved Quesion                   Download File

Thursday, August 11, 2016

class8 Cell structure and function living science question answer

A. MULTIPLE-CHOICE QUESTIONS: Choose the most appropriate answer.

1. Which of these is multicellular?

a. Paramecium b. Amoeba c. bacteria d. mushroom

2. The egg of a hen is a

a. cell. b. tissue c. organ d. organ system

3. Which of these is not present in an animal cell?

a. mitochondria b. nucleus c. cell membrane d chloroplasts

4. Which of these is the control centre of the cell?

a. nucleus b. cytoplasm c. mitochondria d. protoplasm

5. Which organelles are responsible for energy production in a cell?

a. vacuoles b. chloroplasts c. mitochondria d. Golgi bodies

6. Which of these is not stated by the cell theory?

a. Cells are the basic structural units of living organisms. b. All cells are identical.

C. New cells are formed due to division in old cells.

d. The way an organism functions depends on the way the cells work.

7. In which of these does a single cell NOT perform all life functions?

a. Amoeba b. mosquito c. bacteria d. Euglena

8. Which of these unicellular organisms has no definite shape?

a. Amoeba b. Paramecium c. Euglena d. bacteria

Answer: 1. d 2.a 3.d 4.a 5. c 6. d 7. b 8. a

B. VERY SHORT-ANSWER (ZUESTIONS: Give one-word answers.

1. All living organisms are made up of one or more -------------.

2. Which is the largest known single cell?

3. What is the jellylike substance present in cells called?

4. The cell membrane which surrounds the cell does not allow anything to pass through it. True or false?

5. The cytoplasm and the nucleus together make up the

6. Name the cell organelles that help to get energy from food.

7. Which of these has a cell wall—plant cell or animal cell?

8. Name the process by which new cells are formed. Which structure in the nucleus is a storehouse for information needed by the cell to function?

9. Plant cells have large vacuoles as compared to animal cells. True or false?

Ans: 1. cells 2. An ostrich egg 3. Cytoplasm 4. False 5. protoplasm 6. Mitochondria

7. Plant cell 8. Cell division 9. Genes 10. protoplasm

C. SHORT-ANSWER QUESTIONS (TYPE I): Answer in a sentence or two.

1. What are the 'building blocks of life'? Why are they so called?

Ans: Cells are the building blocks of life. They are so called because all living things are made up of one or more cells.

2 . Differentiate between unicellular and multicellular organisms.

Ans: Organisms which are made up of only one cell are called unicellular organisms. eg. amoeba.

Organisms which are made up of more than one cell are called Multicellular organisms eg. man

68. What is cytoplasm?

Ans: Cytoplasm is a jelly-like substance that makes up most of the inside of a cell. All life functions take place in the cytoplasm. lt is divided into two parts:

(i) Cytosol: It is the soluble part of the cytoplasm and (ii) Cell organelles.

4. What do you mean by protoplasm?

Ans: The nucleus and the cytoplasm together make up living substance of the cell and referred as protoplasm .

5. What is a tissue?

Ans: A group of cells similar in functions is called tissue cells. For example muscular tissue which help in movement of our body.

6. What are organelles?

Ans: Small living structures present in the cytoplasm of a cell which perform different function are called organelles eg. Mitochondria that oxidised food to release energy.

D.SHORT-ANSWER QUESTIONS (Type II): Answer in about 30 words.

1. What are the lower levels of organization in a multicellular organism? Are these levels also present in unicellular organisms?

Ans: The lower levels of organization in a multicellular organism are as follows:

Cells - > Tissues -> Organs -> Organ Systems ---> Organism

These levels are not present in unicellular organisms

2. Draw a labelled diagram to show the general structure of a cell. [see book]

3. What are the differences between plant and animal cells?

Ans: Plant Cell (i) Large in size. (ii) Cell wall is present (iii) Plastids are present. (iv) Plant cell usually has one or two large vacuoles.

Animal Cell (i) generally, small in size. (ii) Cell wall is absent. (iii) Plastids are absent. (iv) Vacuoles are either absent or are very small.

4. What is meant by the term cell division? Why is cell division necessary?

Ans: The process by which new cells are formed from the old existing cells are known as cell division. The new cells formed in this way are known as daughter cells.

Cell division is necessary: (i) for replacement of dead cells (ii) for the growth of an organism.

E. LONG-ANSWER QUESTIONS: Answer in about 60 words.

1. What are the main points of the cell theory of life?

Ans: 1. The main points of the cell theory of life given by M. Schleiden and T. Schwann are:

(i) All living things are made up of cells

(ii) All cells are similar in their basic structure and function but are not identical. They differ in size and structure.

(iii) New cells are formed due to division in old cells.

(iv) The organization of cells in the body of a living organism determines its structure.

(v) The way an organism functions depends on the way the cells work.

2. What are the functions of the following in a cell?

a. cell membrane b. cytoplasm C. nucleus d. chromosomes e. mitochondria f. vacuoles

Ans: The functions of the following in a cell are:

(a) Cell membrane: (i) It protects the cell and gives it a shape. (ii) It allows water, minerals and some other necessary substances to pass through it.

(b) Cytoplasm:(i) It acts as a store of vital chemical molecules such as amino acids, glucose, vitamins, ions, etc.

(ii) All life functions take place in the cytoplasm.

(c) Nucleus: (i) It controls all metabolic activities of cell. (ii) It regulates cell cycle and directs growth. (iii) It also transmits the hereditary characters from parents to offspring.

(d) Chromosomes: Chromosomes carry genes which contain all the information needed by the cell to function and to reproduce further cells of the next generation. Thus, genes transfer characteristics from the parent to the offspring.

(e) Mitochondria: They oxidize food to provide energy. Thus, they are called powerhouse of the cell.

Vacuoles: (i) They store food, water and wastes. (ii) They help to maintain the osmotic pressure in a cell.

(iii) They provide turgidity and rigidity to the plant cells.

3. With the help of examples, show the variation in shapes and sizes of cells. `

Ans: Cells have different jobs to do, and therefore have different shapes and sizes.

For example, nerve cells have fibres that may be more than one meter long. Messages pass from one nerve cell to another along these fibres.

Muscle cells are long and thin. This helps the muscle cells in expansion and contraction. White blood cells can change their shape, and this helps them to destroy germs. Plant cells located on the outer part of the stem have thick walls for support. Some cells in plants are used to store food, and these cells are larger than other cells.

HOTS UESTIONS: Think and answer.

1. In general, exit sizes are not related to the size of an organism. However, will there be a difference in the length of the nerve Cells in a rat and a giraffe?

Ans: Since the spinal cord of a giraffe is much longer (up to 2.6 m) than that of a rat, the nerve cells are also longer.

2. White Blood Cells can squeeze through walls of blood vessels and get into intercellular spaces to fight against germs. Which property of WBCs allows them to do this?

Ans: White blood cells have the ability to change their shape. This helps them to squeeze through walls of blood vessels and get into intercellular spaces.

3. Why do plant cells need a cell wall, and animal cells do not?

Ans: Plant cells need a cell wall to maintain cell shape and rigidity. This rigidity allows plants to stand upright without the need for bones. In other hand animals have skeletons for this purpose and do not need a cell wall.

Also absence of a cell wall gives animals’ greater mobility. Plants do not need to move around.

4. Why do you think parents and doctors get very worried if a child gets a head or spinal injury?

Ans: Most nerve cells cannot be replaced by cell division once they die. Therefore the central nervous system cannot be healed if there is an injury to it. That is why an injury to the nervous system is very worrying. (Recent research has shown that some nerve cells can be replaced by the body.)

5. Living things are made up of cells while non-living things are made up of atoms and molecules. Do you agree? Give reasons.

Ans: I do not entirely agree since living and non-living things are both made up of atoms and molecules. The difference is that the basis structural units are different — cells in living and atoms or molecules in non-living. Cells themselves are made up of atoms and molecules, and one or more cells together make up a living thing.

Cell first observed 
Robert Hooke, an English scientist, discovered a honeycomb-like structure in a cork slice using a primitive compound microscope. He only saw cell walls as this was dead tissue. He coined the term "cell" for these individual compartments he saw.

First living cells seen 
Anton van Leeuwenhoek, a Dutch biologist, looks at pond water with a microscope he made lenses for.

Miniature animals 
Anton van Leeuwenhoek made several more discoveries on a microscopic level, eventually publishing a letter to the Royal Society in which he included detailed drawings of what he saw. Among these was the first protozoa and bacteria discovered.

The center of the cell seen 
Robert Brown, an English botanist, discovered the nucleus in plant cells.

Basic building blocks 
Matthias Jakob Schleiden, a German botanist, proposes that all plant tissues are composed of cells, and that cells are the basic building blocks of all plants. This statement was the first generalized statement about cells.

Cell theory 
Theodor Schwann, a German botanist reached the conclusion that not only plants, but animal tissue as well is composed of cells. This ended debates that plants and animals were fundamentally different in structure. He also pulled together and organized previous statement on cells into one theory, which states: 1 - Cells are organisms and all organisms consist of one or more cells 2 - The cell is the basic unit of structure for all organisms

Where does life come from 
Albrecht von Roelliker discoveres that sperm and eggs are also cells.

Basic unit of life 
Carl Heinrich Braun reworks the cell theory, calling cells the basic unit of life.

3rd part to the cell theory added 
Rudolf Virchow, a German physiologist/physician/pathologist added the 3rd part to the cell theory. The original is Greek, and states Omnis cellula e cellula. This translates as all cells develop only from existing cells. Virchow was also the first to propose that diseased cells come from healthy cells.

Tuesday, August 9, 2016

Class7 chapter Soil Living science question answer

A. MULTIPLE-CHOICE QUESTIONS: Choose the most appropriate answer.
1. Humus and the smallest particles of rock form the
a. A-horizon. b. B-horizon. c. C-horizon. d. bedrock

2. Which of these has the smallest size of particles? 
a. sand b. silt c. clay d. gravel

3. Which type of soil is best for growing cotton? 
a. sandy b. clayey c. loamy d. sandy-loam

4. Which of these does not cause weathering'?

a. clouds b. wind c. flowing water d. freezing of rainwater

5. Water percolating into the soil collects over

a. A-horizon. b. B-horizon. c. C-horizon. d. none of these

6. Water logging can be expected in soil which is rich in a. sand. b„ clay. c. silt. d. humus.

7. Paddy grows best in a. clayey soil. b. loam. c. sandy soil. d. sandy-loam.

Answer. 1. a 2. c 3. d 4. a 5. d 6. b 7. a

B. VERY SHORT-ANSWER QUESTIONS: Give one-word answers.
1. Breaking down of rock into smaller pieces by natural forces is called ----.

2. Which absorbs more water—sandy soil or clay?

3. The layer of soil that contains the largest rock pieces is called ---.

4. in general, which is the best topsoil for growing plants'?

5. Water logging occurs in sandy soil. True or false?

6. Is soil a natural resource'?

7. Since clay holds more water, it is very good for plants as they get plenty of water. True or false?

8. Humus is formed by the action of insect on soil. True or false?

9. Soil without humus cannot be fertile. True or false?

10. Humus is formed bar the action of decomposers. True or false? .

Answer: 1. weathering 2. sandy soil 3. bedrock 4. loam 5. false 6. yes 7. false 8. false 9. True 10. true

C. SHORT-ANSWER QUESTIONS: Answer in a sentence or two.
1. What does soil consist of?

Ans: Soil consists of mineral particles, humus, air, water and living organisms.

2. What is weathering?

Ans: Weathering is the breaking down of huge pieces of rocks into smaller pieces by the action of natural forces, such as water, glaciers, wind, roots of plants etc.

3. Which soil will allow more water to percolate—sandy soil or clayey soil? Why?

Ans: Sandy soil will allow more water to percolate. This is because water drains quickly through large spaces between the sand particles.

4. Which soil will absorb more water—sandy soil or clayey soil? Why?

Ans: clayey soil will absorb more water. In clayey soil, which mostly contains clay, water drains through very slowly, since the particles are very small and tightly packed.

5. What is humus?

Ans: The dead and decay remains of plants and animals present in soil is called humus

6. How does large variation between day and night temperatures cause weathering?

Ans: The rocks expand during the day and contract at night. This constant expansion and contraction weakens the rocks, and they crack and crumble.

7. What do you mean by 'water table'?

Ans: Rainwater that percolates through the soil collects above the bedrock. This natural level of groundwater is called the water table.

D. LONG-ANSWER QUESTIONS: Answer in about 50 words.
1. Explain how water is responsible for the formation of soil.

Ans: Rainwater enters crevices of rocks. In winters, as this water freezes, it expands. This expansion breaks the rocks into smaller pieces. The broken pieces roll down by the force of flowing water and they collide against the ground and against each other to break down further. Finally, they get converted into very fine particles and mix with humus to form soil.

2. Trees help in soil formation as well as in its protection. Explain.

Ans: Roots of trees growing through rocks exert great pressure on the rocks. This causes cracks in the rocks, leading

to weathering. On the other hand, roots of plants growing on slopy hilly areas hold soil tightly and prevents soil erosion. Thus, we can say that trees help in soil formation as well as in its protection.

3. Name the different lavers of soil. What does each layer consist of?

Ans: The different layers of soil are

(i) Top soil (A-horizon): Humus and the smallest particles of rock form the upper layer of soil called topsoil or A-horizon. It contains the most nutrients for plants.

(ii) Sub soil (B-horizon): It is mostly made up of rock bits and some nutrients, such as soluble minerals and iron oxides.

(iii) Parent rock (C-horizon): It consists of small pieces of rocks with cracks and crevices.

4. Distinguish between clay, silt and sand.

Ans: (i) Clay has the smallest size of particles less than 0.002 mm in diameter. In fact, we cannot see a single clay particle. Clay feels smooth because of its small particle size.

(ii) Silt has particles larger than clay, (diameter between 0.002 mm and 0.2 mm). Therefore, it is not so smooth. It can be found, for example, in a river bed.

(iii) Sand has the largest-sized particles, which can easily be seen (diameter greater than 0.2 mm). They are coarse to touch.

5. What is loam? Why is it considered to be the best topsoil for growing plants?

Ans: The best topsoil for growing plants is loam. Loam is a mixture of sand, silt and clay and also has humus in it. It has the right water-holding capacity for plant growth. It also has adequate spaces between the soil particles to trap air required by the roots of the plants.

6. Why is soil regarded as our most important natural resource?

Ans: .(i) Soil is our most important natural resource. It is useful to us in many ways: We depend on the soil for food, clothing and shelter: By supporting growth of plants, the soil provides us with food. Much of our clothing, such as cotton and wool, can be traced to the soil. Plants also provide us with the medicines, fuel, paper and wood which is used in making furniture and for constructing houses.

(ii) We depend on the soil for minerals: Industries use the minerals dug out from the earth.to extract metals, such as iron, gold, silver and so on. These are used in thousands of industries that produce various useful things for us. (iii) We depend on the soil for water: Water that seeps into the soil is stored underground as subsoil water. We use this water for drinking and other purposes

7. Why is the earthworm referred to as 'farmer's friend'?

Ans: The earthworm makes burrow in the soil. This makes the soil loose thus allowing air into it and water to drain from it. Earthworm also forms channels in the soil for the root to spread through. For this reason, the earthworm is referred to as the 'farmer's friend'.

E. HOTS QUESTIONS: Think and answer.
1. What effect does construction of buildings and roads have on water percolation through soil? Hence what effect would this have on the water table?

Answer: Construction of buildings and roads stops water percolation through the soil. This causes the water table to go down.

2, Soil is constantly formed by weathering of rocks. Why then are we so concerned about soil erosion?

Answer: Formation of 1 cm of soil by natural method may take 100 years or more. However, erosion of soil happens in a matter of days. That is why soil erosion is of great concern.

3. Why does topsoil have much more humus than subsoil?

Answer: The decay of the remains of plants and animals that forms humus mostly happens on top of the soil. Therefore the humus formed remains mostly on the top soil.

4. What kind of soil is most suitable for making toys and why?

Answer: Clayey soil is smooth and sticky. It does not crumble apart easily. So it is most suitable for making toys as it can be moulded into any shape without breaking.

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